1. Field of the Invention
The present invention relates to an air intake manifold for an engine. More particularly, the present invention relates to an engine air intake manifold having first and second main body sections that are divided along an airflow direction and form an air intake passage therebetween. The first and second main body sections have oppositely facing mating parts that form a gas passage for supplying a secondary additive gas to the intake air flowing inside the air intake manifold. Preferably, the engine air intake manifold includes an air intake branch pipe with a mounting block for mounting an air intake control valve that is inserted into a downstream portion of the air intake branch pipe.
2. Background Information
An air intake manifold for a multiple cylinder engine generally has a collector into which intake air is introduced to the cylinders. The air intake manifold has a plurality of air intake branch parts that distribute the air from the collector to the cylinders. When this kind of air intake manifold is used, a secondary additive gas (e.g., blow-by gas, EGR gas, or secondary air) is sometimes added to the main flow of air in order to reduce atmospheric pollutants in the exhaust gas and accomplish idle control. When blow-by gas, EGR gas, secondary air or other secondary additive gas is circulated with the engine intake air, it is generally introduced at the collector of the air intake manifold. However, if the engine has multiple cylinders, it is difficult to distribute the secondary additive gas to all the cylinders evenly and, since the position where the secondary additive gas is introduced is far from the cylinders, it is difficult to improve the control response of the secondary additive gas.
Consequently, as disclosed in Japanese Laid-Open Patent Publication No. 5-030412 and Japanese Laid-Open Patent Publication No. 2000-008968, there have been several attempts to introduce the secondary additive gas separately to each cylinder from downstream positions of the air intake branch pipes of the air intake manifold. More specifically, Japanese Laid-Open Patent Publication No. 5-030412 (pages 7 to 8, FIG. 3) discloses a configuration in which gas passages for delivering blow-by gas to each individual cylinder are provided in a mounting flange that is used for mounting the air intake manifold to the engine main body. On the other hand, Japanese Laid-Open Patent Publication No. 2000-008968 (pages 4 to 5, FIGS. 6 and 7) presents a configuration in which a spacer is arranged between the air intake manifold and the engine and gas passages for delivering EGR gas to each individual cylinder are provided in the spacer.
Moreover, an air intake manifold has been configured to introduce a secondary additive gas into the air intake passage of each air intake branch part in which a gas distribution pipe arranged on the outside of the air intake branch parts and gas passages that run from the gas distribution pipe to the air intake passages of the air intake branch parts.
More specifically, the air intake manifold described in Japanese Laid-Open Patent Publication No. 2001-123901 (pages 3 to 5, FIG. 2) has a gas distribution pipe that is arranged inside the collector and provided with a plurality of discharge openings corresponding to the entrances of the air intake passages of the air intake branch parts.
Also, Japanese Laid-Open Patent Publication No. 2001-123901 (pages 3 to 5, FIG. 2) discloses an air intake manifold in which an EGR gas distribution pipe that is arranged inside the collector and provided with a plurality of discharge openings or holes corresponding to the entrances of the air intake passages of the air intake branch parts in order to distribute the EGR gas uniformly to the all of the cylinders. The EGR gas distribution pipe is arranged inside the collector along the direction in which the cylinders are lined up and has discharge openings or holes in positions corresponding to the air intake branch pipes. This air intake manifold efficiently distributes EGR gas to the cylinders by blowing EGR gas toward the entrance of the air intake passages from the discharge openings of the gas distribution pipe located inside the collector.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved air intake manifold for an engine. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.